Catapult case

Jan:Are you looking for PPT instructions? When I’m training, I just run all of these matters informally, by setting up teams and factors in Minitab on the fly.MSA can be done a number of ways, but there are probably better exercises for GR&R, if that’s what you are trying to tackle. AAA can be done by using the catapult with observers, but since the catapult exercise is a “destructive test” it’s impossible to get repeatibility.If you want to chat about all of this, drop me a line and a number.Warm regards,Jonathan Leahey
Pres. LCG, LLC

Its not impossible to get repeatibility

Cyrus:Perhaps I wasn’t clear. If you read my missive, what I was saying is that you would be hard pressed to do measurement systems analysis with the catapult.Why? If you were using observers to record where the ball landed to compare their results, you couldn’t replicate the ball landing in the same exact spot every shot. If you argue that you can, I would surmise that your measurement system lacks discrimination.I’ve done several DOE’s with catapults of all sorts. That shouldn’t be a problem. In fact, if you use Mintab’s byzantine structure to set up a GFF, FF, etc., the exercise is a great way to select factors and take a class through the data set-up protocol.Hope this helps.Let me know if I can be of further assistance.Regards,
Jonathan

We used aluminum foil in the target area to get the mark of the projectile landing.  Then the MSA had to include the operational definition of how to measure (front of dent?, middle, back ..etc) to ensure consistency.
M

When I did the catapult exercise, are final target was a coffee cup placed at the prescribed distance.  So the aluminum foil method wouldn’t work since we had to factor in the elevation and circumference of the cup’s rim.  We ended up getting a 10 ft length of plastic gutter liner (approximately the same diameter as the cup) and filling it to the appropriate height with sand.  That way we could determine preceisely where the ball would hit the rim. 

As far as the off center problem went, we affixed a laser level to the front of the catapult for both aiming and aligning purposes.  Using the laser as the centerpoint, you could draw parallel lines 2″ or so on either side to measure lateral accuracy as well as distance accuracy.  It would also be important to secure the catapult so its not drifting shot to shot.